Light emitting device

ABSTRACT

Disclosed are a light emitting device. A light emitting diode comprises a light emitting device comprises a plurality of N-type semiconductor layers including a first N-type semiconductor layer and a second N-type semiconductor layer on the first N-type semiconductor layer, an active layer on the second N-type semiconductor layer, and a P-type semiconductor layer on the active layer, wherein the first N-type semiconductor layer comprises a Si doped Nitride layer and the second N-type semiconductor layer comprises a Si doped Nitride layer, and wherein the first and second N-type semiconductor layers have a Si impurity concentration different from each other.

This application is a continuation of application Ser. No. 13/046,520,filed on Mar. 11, 2011 now U.S. Pat. No. 8,258,525, that is acontinuation of application Ser. No. 12/107,256, filed on Apr. 22, 2008,now U.S. Pat. No. 7,928,454 that claims priority under 35 U.S.C. §119 ofKorean Patent Application No. 10-2007-0039534, filed on Apr. 23, 2007,the entire contents of which are hereby incorporated by reference andfor which priority is claimed under 35 U.S.C. §120.

BACKGROUND

The embodiment relates to a light emitting diode and a method formanufacturing the same.

A light emitting diode is formed by sequentially stacking a bufferlayer, an unintentionally doped GaN layer (Un-GaN layer), an N-type GaNlayer, an active layer, and a P-type GaN layer on a substrate.

The light emitting diode has a characteristic in which electrons areinserted into holes on the active layer to emit light if power isapplied to the N-type GaN layer and the P-type GaN layer.

Meanwhile, since the substrate has a lattice constant different fromthat of the N-type GaN layer, dislocation may occur, and the bufferlayer and the Un-GaN layer reduce a difference between lattice constantsof the substrate and the GaN layer.

However, the buffer layer and the Un-GaN layer have a limitation in thereduction of the difference of the lattice constants, and thedislocation density may be increased due to the Un-GaN layer.

SUMMARY

The embodiment provides a light emitting device and a method formanufacturing the same.

The embodiment provides a light emitting device and a method formanufacturing the same, capable of reducing dislocation density.

The embodiment provides a light emitting device and a method formanufacturing the same, capable of reducing lattice mismatching, therebyimproving a light emitting characteristic.

According to the embodiment, a light emitting device comprises aplurality of N-type semiconductor layers including a first N-typesemiconductor layer and a second N-type semiconductor layer on the firstN-type semiconductor layer; an active layer on the second N-typesemiconductor layer; and a P-type semiconductor layer on the activelayer, wherein the first N-type semiconductor layer comprises a Si dopedNitride layer and the second N-type semiconductor layer comprises a Sidoped Nitride layer, and wherein the first and second N-typesemiconductor layers have a Si impurity concentration different fromeach other.

According to the embodiment, a light emitting device comprises aplurality of N-type semiconductor layers including a first N-typesemiconductor layer and a second N-type semiconductor layer on the firstN-type semiconductor layer; an active layer on a first portion of thesecond N-type semiconductor layer; a P-type semiconductor layer on theactive layer, a first electrode on a second portion of the second N-typesemiconductor layer; and a second electrode on the P-type semiconductorlayer, wherein the first N-type semiconductor layer comprises a Si dopedNitride layer and the second N-type semiconductor layer comprises a Sidoped Nitride layer, and wherein the first and second N-typesemiconductor layers have a Si impurity concentration different fromeach other.

According to the embodiment, a light emitting device comprises asubstrate; a first N-type semiconductor layer including a GaN layer onthe substrate; a second N-type semiconductor layer including a GaN layeron the first N-type semiconductor layer; an undoped GaN layer on thesecond N-type semiconductor layer; an active layer on the undoped GaNlayer; and a P-type GaN layer on the active layer, wherein the first andsecond N-type semiconductor layers have a Si impurity concentrationdifferent from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view used to explain a light emitting diode according to thefirst embodiment; and

FIG. 2 is a view used to explain a light emitting diode according to thesecond embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description of the embodiments, when layers (films), regions,patterns, or elements are described in that they are formed on or undersubstrates, layers (films), regions, or patterns, it means that they areformed directly or indirectly on or under the substrates, layers(films), regions, or patterns.

The thickness and size of each layer shown in the drawings can besimplified or exaggerated for the purpose of convenience or clarity. Inaddition, the elements may have sizes different from those shown indrawings in practice.

Hereinafter, a light emitting diode and a method for manufacturing thesame with reference to accompanying drawings.

FIG. 1 is a view used to explain a light emitting diode according to afirst embodiment.

The light emitting diode according to the first embodiment comprises asubstrate 10, a buffer layer 20, a first Un-GaN layer 31, a first N-typeGaN layer 32, a second Un-GaN layer 33, a second N-type GaN layer 34, anactive layer 40, a P-type GaN layer 50, and an ohmic electrode layer 60.A first electrode layer 70 is formed on the second N-type GaN layer 34,and a second electrode layer 80 is formed on the ohmic electrode layer60.

As shown in FIG. 1, the light emitting diode according to the firstembodiment includes the first and second Un-GaN layers 31 and 33 and thefirst and second N-type GaN layers 32 and 34, which are alternativelyand repeatedly stacked on the buffer layer 20.

As shown in FIG. 1, the Un-GaN layer and the N-type GaN layer arerepeated twice.

According to the first embodiment, the first N-type GaN layer 32 isformed between the first and second Un-GaN layers 31 and 33, therebypreventing the occurrence of a dislocation density due to the first andsecond Un-GaN layers 31 and 33. According to the first embodiment, aplurality of Un-GaN layers are provided, in which each Un-GaN layer isthinner than an Un-GaN layer provided in a single layer structure of theUn-GaN layer and an N-type GaN layer according to the related art.Similarly, each N-type GaN layer may be thin a conventional N-type GaNlayer.

In other words, the increase of dislocation density occurring as theUn-GaN layer becomes thick is prevented by forming a plurality of thinUn-GaN layers.

For example, the first and second Un-GaN layer 31 and 33 may havethicknesses in the range of 0.5 μm to 1 μm, and the first and secondN-type GaN layers 32 and 34 may have thicknesses in the range of 1 μm to1.5 μm.

According to the first embodiment, the dislocation density of the firstand second N-type GaN layers 32 and 34 is reduced as the N-type GaNlayers become close to the active layer 40, that is, distant from thebuffer layer 20.

To this end, the first and second Un-GaN layers 31 and 33 and the firstand second N-type GaN layers 32 and 34 are formed in a chamber having ahigher temperature and a lower pressure while reducing the amount ofTMGa flowed into the chamber as the Un-GaN layers and the N-type GaNlayers are close to the active layer 40.

Further, since a dislocation density may be increased as theconcentration of impurities is increased in the first and second N-typeGaN layers 32 and 34, the concentration of N-type impurities isdecreased as the N-type GaN layers become close to the active layer 40.

FIG. 2 is a view used to explain a light emitting diode according to asecond embodiment.

The light emitting diode according to the second embodiment comprises asubstrate 10, a buffer layer 20, a first Un-GaN layer 31, a first N-typeGaN layer 32, a second Un-GaN layer 33, a second N-type GaN layer 34, athird Un-GaN layer 35, a third N-type GaN layer 36, an active layer 40,a P-type GaN layer 50, and an ohmic electrode layer 60. A firstelectrode layer 70 is formed on the third N-type GaN layer 36, and asecond electrode layer 80 is formed on the ohmic electrode layer 60.

As shown in FIG. 2, the light emitting diode according to the secondembodiment has the first, second, and third Un-Ga layers 31, 33, and 35and the first, second, and third N-type GaN layers 32, 34, and 36alternatively stacked on the buffer layer 20.

As shown in FIG. 2, the Un-GaN layers and the N-type GaN layers arerepeated three times.

Although it is not shown, the Un-GaN layers and the N-type GaN layersmay be repeated four times according to another embodiment.

According to the second embodiment, the first and second N-type GaNlayers 32 and 34 are alternately provided in relation to the first,second, and third Un-GaN layers 31, 33, and 35, thereby preventing theincrease of dislocation density by the first, second, and third Un-GaNlayers 31, 33, and 35. According to the second embodiment, a pluralityof Un-GaN layers are provided. In this case, the first, second, andthird Un-GaN layers 31, 33, and 35 are thinner than an Un-GaN layerprovided in a single layer structure of the Un-GaN layer and an N-typeGaN layer according to the related art. Similarly, the first, second,and third N-type GaN layers 32, 34, and 36 may be thin a conventionalN-type GaN layer.

In other words, the increase of dislocation density occurring as theUn-GaN layer becomes thick is prevented by forming a plurality of thinUn-GaN layers.

For example, the first, second, and third Un-GaN layers 31, 33, and 35may have thicknesses in the range of 0.3 μm to 0.6 μm, and the first,second, and third N-type GaN layers 32, 34, and 36 may have thicknessesin the range of 0.5 μm to 1 μm.

According to the second embodiment, the dislocation density of theN-type GaN layer is reduced as the N-type GaN layer becomes close to theactive layer 40, that is, distant from the buffer layer 20.

To this end, the Un-GaN layer and the N-type GaN layer are formed in achamber having a higher temperature and a lower pressure while reducingan amount of TMGa flowed into the chamber as the Un-GaN layer and theN-type GaN layer are close to the active layer 40.

Further, since a dislocation density may be increased as theconcentration of impurities is increased in the first, second, and thirdN-type GaN layers 32, 34, and 36, the concentration of N-type impuritiesis decreased as the N-type GaN layers become close to the active layer40.

As described above, in the light emitting diode according to theembodiments, a plurality of thin Un-GaN layers are provided, and theN-type GaN layers are provided between the Un-GaN layers in order toprevent the increase of dislocation density caused by the Un-GaN layers.Accordingly, the increase of the dislocation density in the Un-GaN layercan be prevented due to the N-type GaN layer.

In addition, the light emitting diode according to the embodiments isprovided such that dislocation density is decreased as the N-type GaNlayer becomes close to the active layer 40.

Accordingly, the dislocation density of the N-type GaN layer in contactwith the active layer 40 is decreased so that the light emittingcharacteristic of the light emitting diode can be improved.

Hereinafter, a method for manufacturing the light emitting diodeaccording to the embodiment will be described in detail with referenceto FIG. 2.

The buffer layer 20 is formed on the substrate 10. For example, thesubstrate 10 includes at least one of Al₂O₃, Si, SiC, GaAs, ZnO, andMgO.

The buffer layer 20 is used to reduce a difference between latticeconstants of the substrate 10 and the GaN layer stacked on the substrate10. For example, the buffer layer 20 may have a stacking structure suchas AlInN/GaN, In_(x)Ga_(1-x)N/GaN, orAl_(x)In_(y)Ga_(1-x-y)N/In_(x)Ga_(1-x)N/GaN.

For example, the buffer layer 20 may be grown by flowing TMGa and TMInat a flow rate of 3×10⁵ Mol/min into the chamber, in which the substrate10 is positioned, and flowing TMAl at a flow rate of 3×10⁶ Mol/min intothe chamber together with hydrogen gas and ammonia gases.

The first Un-GaN layer 31, the first N-type GaN layer 32, the secondUn-GaN layer 33, the second N-type GaN layer 34, the third Un-GaN layer35, the third N-type GaN layer 36 are sequentially formed on the bufferlayer 20. The first, second, and third Un-GaN layers 31, 33, and 35 andthe first, second, and third N-type GaN layer 32, 34, and 36 may beformed through a metal-organic vapor chemical deposition (MOCVD)process.

First, the first Un-GaN layer 31 is formed on the buffer layer 20. Forexample, the first Un-GaN layer 31 may be formed by flowing NH₃(3.7×10⁻² Mol/min) and TMGa (2.9×10⁻⁴-3.1×10⁻⁴ Mol/min) gas in a statein which the chamber is adjusted to have internal pressure of 500 Torrto 700 Torr and the internal temperature in the range of 1040□ to 1050□.

Then, the first N-type GaN layer 32 is formed on the first Un-GaN layer31. For example, the first N-type GaN layer 32 is formed by flowing NH₃(3.7×10⁻² Mol/min), TMGa (2.9×10⁻⁴-3.1×10⁻⁴ Mol/min), a SiH₄ gasincluding N-type impurities such as Si in a state in which a chamber isadjusted to have an internal pressure of 500 Torr to 700 Torr and aninternal temperature the temperature in the range of 1040□ to 1050□.

In this case, the first N-type GaN layer 32 may have a dislocationdensity of 10¹⁰/cm³ or less. In addition, Si may be implanted into thefirst N-type GaN layer 32 with the concentration of 7×10¹⁸/cm².

The second Un-GaN layer 33 is formed on the first N-type GaN layer 32.The second Un-GaN layer 33 is formed by flowing a less amount of TMGagas in a chamber with a lower pressure under a higher temperature ascompared with the process of performing the first Un-GaN layer 31.

For example, the second Un-GaN layer 33 may be formed by flowing NH₃(3.7×10⁻² Mol/min) and TMGa (1.9×10⁻⁴-2.1×10⁻⁴ Mol/min) gas in a statein which a chamber is adjusted to have an internal pressure of 300 Torrto 500 Torr and an internal temperature in the range of 1050° C. to1060° C.

The second N-type GaN layer 34 is formed on the second Un-GaN layer 33.The second N-type GaN layer 34 is formed by flowing a less amount of aTMGa gas and an SiH₄ gas in a chamber with a lower pressure under ahigher temperature as compared with the process of performing the firstN-type GaN layer 32.

For example, the second N-type GaN layer 34 may be formed by flowing NH₃(3.7×10⁻² Mol/min), TMGa (1.9×10⁻⁴-2.1×10⁻⁴ Mol/min), and a SiH₄ gasincluding N-type impurities such as Si in a state in which a chamber isadjusted to have an internal pressure of 300 Torr to 500 Torr and aninternal in the range of 1050□ to 1060□.

In this case, the second N-type GaN layer 34 may have the dislocationdensity of 10⁹/cm³ or less. In addition, Si may be implanted into thesecond N-type GaN layer 34 with the concentration of 5×10¹⁸/cm².

The third Un-GaN layer 35 is formed on the second N-type GaN layer 34.The third Un-GaN layer 35 is formed by flowing a less amount of a TMGagas in a chamber with a lower pressure under a higher temperature ascompared with the process of performing the second Un-GaN layer 33.

For example, the third Un-GaN layer 35 may be formed by flowing NH₃(3.7×10⁻² Mol/min) and TMGa (1.4×10⁻⁴-1.6×10⁻⁴ Mol/min) gas in a statein which a chamber is adjusted to have an internal pressure of 200 Torrto 300 Torr and an internal temperature in the range of 1060° C. to1070° C.

The third N-type GaN layer 36 is formed on the third Un-GaN layer 35.The third N-type GaN layer 36 is formed by flowing a less amount of aTMGa gas and an SiH₄ gas in a chamber with a lower pressure under ahigher temperature as compared with the process of performing the secondN-type GaN layer 34.

For example, the third N-type GaN layer 36 may be formed by flowing NH₃(3.7×10⁻² Mol/min), TMGa (1.4×10⁻⁴-1.6×10⁻⁴ Mol/min), and a SiH₄ gasincluding N-type impurities such as Si in a state in which a chamber isadjusted to have an internal pressure of 200 Torr to 300 Torr and aninternal temperature in the range of 1060° C. to 1070° C.

In this case, the third N-type GaN layer 36 may have the dislocationdensity of 10⁸/cm³ or less. In addition, Si may be implanted into thethird N-type GaN layer 36 with the concentration of 3×10¹⁸/cm².

The active layer 40 is formed on the third N-type GaN layer 36. Forexample, the active layer 40 may have a multi-quantum well structureincluding InGaN/GaN which is grown at a nitrogen gas atmosphere byflowing TMGa and TMIn into the chamber.

The P-type GaN layer 50 is formed on the active layer 40. For example,the P-type GaN layer 50 may be grown by supplying TMGa (7×10⁻⁶ Mol/min),TMAl (2.6×10⁻⁵ Mol/min), (EtCp₂Mg) {Mg (C₂H₅C₅H₄)₂} (5.2×10⁻⁷ Mol/min),and NH₃ (2.2×10⁻¹ Mol/min using hydrogen as a carrier gas.

The ohmic electrode layer 60 is formed on the P-type GaN layer 50. Forexample, the ohmic electrode layer 60 includes at least one of ITO, CTO,SnO₂, ZnO, RuO_(x), TiO_(x), IrO_(x), and Ga_(x)O_(x).

After the above stacking structure is formed, a mask layer (not shown)is formed on the ohmic electrode 60. The ohmic electrode layer 60, theP-type GaN layer 50, the active layer 40, and the third N-type GaN layer36 are selectively etched so that a portion of the third N-type GaNlayer 36 is exposed upward.

The first electrode layer 70 is formed on the third N-type GaN layer 36,and the second electrode layer 80 is formed on the ohmic electrode layer60.

Accordingly, the light emitting diode according to the embodiments canbe manufactured.

In the light emitting diode and the method for manufacturing the sameaccording to the embodiments, the Un-GaN layer and the N-type GaN layerare alternatively stacked, thereby reducing the dislocation density onthe N-type GaN layer adjacent to the active layer.

Further, in the light emitting diode and the method for manufacturingthe same according to the embodiments, a plurality of Un-GaN layers andN-type GaN layers are provided. In this case, the Un-GaN layers and theN-type GaN layers are formed by reducing an amount of TMGa flowed intothe chamber while increasing the temperature of a chamber and reducingthe pressure of the chamber step by step. Accordingly, the dislocationdensity of the N-type GaN layer adjacent to the active layer may be morereduced.

In the light emitting diode and the method for manufacturing the sameaccording to the embodiments, a plurality of Un-GaN layers and aplurality of N-type GaN are formed. In this case, the N-type GaN layeris formed by reducing an amount of N-type impurities step by step.Accordingly, the dislocation density of the N-type GaN layer adjacent tothe active layer can be more reduced.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A light emitting device comprising: a pluralityof N-type semiconductor layers including a first N-type semiconductorlayer and a second N-type semiconductor layer on the first N-typesemiconductor layer; an undoped GaN layer on the second N-typesemiconductor layer; an active layer on the undoped GaN layer; and aP-type semiconductor layer on the active layer, wherein the first N-typesemiconductor layer comprises a Si doped Nitride layer and the secondN-type semiconductor layer comprises a Si doped Nitride layer, whereinthe first and second N-type semiconductor layers have a Si impurityconcentration different from each other, and wherein at least one of thefirst and second N-type semiconductor layers comprises an N-type GaNlayer.
 2. The light emitting device according to claim 1, wherein thesecond N-type semiconductor layer has a Si impurity concentration lowerthan a Si impurity concentration of the first N-type semiconductorlayer.
 3. The light emitting device according to claim 1, wherein theundoped GaN layer is between the second N-type semiconductor layer andthe active layer.
 4. The light emitting device according to claim 1,wherein the first and second N-type semiconductor layers comprise anN-type GaN layer.
 5. The light emitting device according to claim 1,wherein the second N-type semiconductor layer has a dislocation densitylower than a dislocation density of the first N-type semiconductorlayer.
 6. The light emitting device according to claim 1, furthercomprising a first electrode on a first portion of the second N-typesemiconductor layer and a second electrode on the P-type semiconductorlayer.
 7. The light emitting device according to claim 6, furthercomprising an ohmic electrode layer between the second electrode layerand the P-type semiconductor layer.
 8. A light emitting devicecomprising: a plurality of N-type semiconductor layers including a firstN-type semiconductor layer and a second N-type semiconductor layer onthe first N-type semiconductor layer; an active layer on a first portionof the second N-type semiconductor layer; an undoped GaN layer betweenthe second N-type semiconductor layer and the active layer; a P-typesemiconductor layer on the active layer; a first electrode on a secondportion of the second N-type semiconductor layers; and a secondelectrode on the P-type semiconductor layer, wherein the first N-typesemiconductor layer comprises a Si doped Nitride layer and the secondN-type semiconductor layer comprises a Si doped Nitride layer, whereinthe first and second N-type semiconductor layers have a Si impurityconcentration different from each other, and wherein the first andsecond N-type semiconductor layers comprise an N-type GaN layer.
 9. Thelight emitting device according to claim 8, wherein the second N-typesemiconductor layer has a Si impurity concentration lower than a Siimpurity concentration of the first N-type semiconductor layer.
 10. Thelight emitting device according to claim 8, wherein the second N-typesemiconductor layer has a dislocation density lower than a dislocationdensity of the first N-type semiconductor layer.
 11. The light emittingdevice according to claim 8, further comprising an ohmic electrode layerbetween the second electrode layer and the P-type semiconductor layer.12. A light emitting device comprising: a substrate; a first N-typesemiconductor layer including a GaN layer on the substrate; a secondN-type semiconductor layer including a GaN layer on the first N-typesemiconductor layer; an undoped GaN layer on the second N-typesemiconductor layer; an active layer on the undoped GaN layer; a P-typeGaN layer on the active layer; and a first electrode on a first portionof the second N-type semiconductor layer and a second electrode on theP-type GaN layer, wherein the first and second N-type semiconductorlayers have a Si impurity concentration different from each other, andwherein the second N-type semiconductor layer has a Si impurityconcentration lower than a Si impurity concentration of the first N-typesemiconductor layer.
 13. The light emitting device according to claim12, wherein the second N-type semiconductor layer has a dislocationdensity lower than a dislocation density of the first N-typesemiconductor layer.
 14. The light emitting device according to claim12, further comprising an ohmic electrode layer between the secondelectrode layer and the P-type GaN layer.